You already had the $ORACLE_HOME/bin on the PATH environment variable (see ~/.bash_profilehere) so you can issue:

$ netca

Choose Listener Configuration on the Welcome panel:

Select Add as the action:

Type a listener name, I recommend the default "LISTENER":

Select protocols among the available, I choose TCP only:

Choose a listening port, I recommend the default "1521" but you can change it if you want. NOTE: Remember to open this port on iptables if you want remote database access, otherwise you won't be able to use it:

On More Listeners panels, choose No.

If you finish gracefully the wizard, you should be able to see this on the standard output. Observe that the listener is running.